Two objectives were targets of the first year of a 2-year project, designed to provide a methodological baseline for a later study on the relationship in postmenopausal women between Life Styles and Bone Densities. The first objective was to refine the method of bone density measurement with Computerized Axial Tomography (CAT) by: (1) identifying the major sources of variability in the precision of CT scanning and accuracy of bone density measurement, (2) devising means of achieving accurate long-term, high-precision bone density measurements at the lowest possible radiation. To this end glass rod phantoms were employed to calibrate the machine and heavy tungsten filters were used to remove most of the lower energy x-rays. The use of filters produced a more nearly monochromatic beam and reduced the x-ray dose of each scan to about 80 mrem. With the reduction in x-ray dose, three separate scans could be used for each measurement of bone density to average out the variability due to longitudinal positioning of the limb and thus increase the precision of the method. The second objective was to recruit postmenopausal volunteers and characterize them with respect to specific epidemiological parameters -- that, on analysis, may be correlated with the density values in long bones. The volunteers were successfully recruited and are now being processed for the relevant data.